JP2005085803A - Susceptor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a susceptor or a susceptor-cooling system that can uniformly cool the surface of a wafer, by canceling the temperature difference which occurs in a refrigerant flowing down through a refrigerant flow passage. <P>SOLUTION: The refrigerant flow passage 3, composed of a plurality of annular paths 18a-18c, is formed in the susceptor by partitioning an annular hollow section formed in the susceptor by C-shaped partition strips 16a and 16b. The refrigerant flow passage 3 is constituted so that a refrigerant flowing down through two adjacent annular paths of the annular paths 18a-18c flows in opposite directions (flows as counterflows) at distances on both sides of the C-shaped parting strips 16a and 16b. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is a semiconductor wafer manufacturing process (plasma dry etching, via opening, cleaning, via inner surface coating by CVD, etc.), and further in a manufacturing process of liquid crystal (LCD), Electro-Luminescence (EL), solar cell, etc. In particular, the present invention relates to a susceptor or a susceptor cooling system capable of uniformly cooling a target object such as a mounted wafer.

  In an apparatus for performing an etching process on a semiconductor wafer (dry etching process, film formation by chemical vapor deposition, plasma cleaning of the wafer surface, etc.), the susceptor that supports the wafer that is the object to be processed has a static function as an original function. It has an electric chuck function and a function as a lower electrode.

  Furthermore, the susceptor needs to have a cooling function in addition to the functions described above, and not only can the wafer be simply cooled, but also must be cooled so that the surface temperature is uniform. It becomes. When etching is performed, plasma is generated between a plasma generation source disposed above the susceptor and a lower electrode disposed on the susceptor upper surface, and ions and the like collide with the wafer surface held on the susceptor. This is because the surface of the wafer is heated, but in order to improve the yield of the product, it must be cooled so that the surface temperature becomes uniform.

  For this reason, in the conventional susceptor, various contrivances have been made for the structure of the coolant channel so that the temperature on the wafer surface is as uniform as possible (for example, JP-A-7-245297 and JP-A-2002-343854). Issue gazette).

Japanese Patent Laid-Open No. 7-245297 JP 2002-343854 A

  However, in the conventional susceptor, the temperature difference of the refrigerant that occurs in the circumferential direction around the axis of the susceptor cannot be eliminated. Therefore, there is a certain limit in trying to cool the wafer surface uniformly. there were.

  The present invention has been made to solve such a problem of the prior art, eliminates the temperature difference in the refrigerant flowing down in the refrigerant flow path, and as a result, can uniformly cool the wafer surface. Aims to provide a susceptor cooling system.

  In the susceptor according to the present invention, an annular hollow portion formed inside is partitioned by a C-shaped partition plate, whereby a refrigerant flow path including a plurality of annular paths is formed inside, and the plurality of those Among the annular passages, the refrigerant flowing down two adjacent annular passages is configured to flow in opposite directions to each other across the C-shaped partition plate (flow as an opposing flow). It is said. In this case, since heat exchange is performed through the partition plate, the temperature difference of the refrigerant in the circumferential direction around the support shaft is eliminated, and as a result, the susceptor or the object to be processed (wafer or the like) is uniform. Cooling can be achieved.

  Two or more C-shaped partition plates are arranged, and they are preferably arranged on a concentric circle of an imaginary circle centered on the axis of the susceptor. It is preferable that heat transfer fins for increasing the heat area are respectively disposed.

  Moreover, it is preferable that the susceptor according to the present invention is configured such that a gas-liquid mixed phase refrigerator refrigerant is directly supplied to the refrigerant flow path. In this case, it is preferable to use HFC type refrigerator refrigerant, hydrocarbon refrigerator refrigerant, carbon dioxide, or ammonia as the refrigerator refrigerant supplied into the refrigerant flow path. Further, it is preferable that “refrigeration of the liquid phase refrigerant” that is an evaporation process of the refrigeration cycle is performed in the refrigerant flow path, and the susceptor functions as an evaporator.

  A hollow portion inside the susceptor is partitioned by a C-shaped partition plate, thereby forming a refrigerant flow path composed of a plurality of annular paths, and among the plurality of annular paths, the refrigerant flowing down two adjacent annular paths, When configured to flow in opposite directions (flowing as counterflows) across the C-shaped partition plate, heat exchange is performed through the partition plate, so the support shaft is the center. The temperature difference of the refrigerant in the circulating direction is eliminated, and as a result, the susceptor or the object to be processed can be uniformly cooled.

  The best mode for carrying out the “susceptor” of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic view of a first embodiment of a susceptor cooling system 1 to which the present invention “susceptor 2” is applied. The susceptor cooling system 1 includes a susceptor 2, a refrigerant flow path 3 formed in the susceptor 2, and a refrigerant supply device 4 that supplies a refrigerant to the refrigerant flow path 3. The susceptor cooling system 1 adopts a direct cooling system, such as a refrigerator refrigerant (HFC type refrigerator refrigerant such as R410A and R407C, hydrocarbon refrigerant refrigerant such as butane, carbon dioxide, ammonia, etc. ) Is directly supplied from the refrigerant supply device 4 to the refrigerant flow path 3.

  The refrigerant flow path 3 of the susceptor 2 is connected to the refrigerant supply device 4 via the refrigerant supply pipe 9 and the refrigerant discharge pipe 10, and the refrigerant supplied from the refrigerant supply device 4 passes through the refrigerant supply pipe 9. Then, while flowing into the refrigerant flow path 3 and flowing down in the refrigerant flow path 3, the heat of the wafer 11 is absorbed (cooled) by boiling heat transfer (evaporation heat transfer), and then discharged from the refrigerant flow path 3. Then, the refrigerant returns to the refrigerant supply device 4 through the refrigerant discharge pipe 10 and circulates.

  The refrigerant supply device 4 includes a compressor 5, a condenser 6, an expansion valve 7, and a hot gas bypass 8 that are basic elements constituting a refrigeration cycle. In addition, in order to construct a refrigeration cycle, an evaporator is required in addition to these elements. In this susceptor cooling system 1, the evaporator is not provided in the refrigerant supply device 4, and will be described later. Thus, the susceptor 2 functions as an evaporator.

  Here, the structure of the susceptor 2 and the refrigerant flow path 3 will be described in detail. FIG. 2 is an enlarged view of a horizontal section of the susceptor 2 shown in FIG. 1, and FIG. 3 is an enlarged view of a vertical section.

  The susceptor 2 is formed by processing a material such as an aluminum alloy. As shown in FIGS. 2 and 3, the susceptor 2 has a cylindrical appearance and has an annular hollow portion inside. Yes.

  Note that, as shown in FIG. 3, an electrode sheet 13 formed to have substantially the same size as the wafer 11 is attached to the upper surface of the susceptor 2. The electrode sheet 13 has a structure in which a conductive film such as a copper foil is bonded to a polyimide resin film, and functions as a lower electrode and has a function of holding the wafer 11 by suction (electrostatic chuck function). .

  A gas supply path 14 is formed at the center of the susceptor 2. Helium gas is supplied to the upper side of the electrode sheet 13 through the gas supply path 14, and a gas layer 15 is formed between the wafer 11 and the electrode sheet 13. The contact thermal resistance between the wafer 11 and the wafer 11 is reduced.

  An annular hollow portion formed inside the susceptor 2 is formed on a virtual circle centered on the axis of the susceptor 2 and two C-shaped partition plates 16 (inner partition plates) arranged on the concentric circles. 16a, the outer partition plate 16b), and the linear partition plate 17 extending in the radial direction, and thereby, three annular passages (an inner annular passage 18a and an intermediate annular passage 18b) are formed inside the susceptor 2. The refrigerant flow path 3 consisting of the outer annular path 18c) is formed.

  Of the three partition plates, the straight partition plate 17 extends from the center side inner wall 19 to the outer peripheral side inner wall 20 of the susceptor 2 and is attached so as to close tightly from the floor surface to the ceiling surface. Thus, the refrigerant introduced into is prevented from flowing over the straight partition plate 17 in the circumferential direction.

  In FIG. 2, 27 is a support shaft of the susceptor 2, 21 is a refrigerant inlet connected to the refrigerant supply pipe 9 shown in FIG. 1, and 22 is a refrigerant outlet connected to the refrigerant discharge pipe 10. It is. The refrigerant inflow port 21 opens at a position close to the connecting portion between the center side inner wall 19 and the straight partition plate 17, while the refrigerant discharge port 22 is connected to the outer peripheral side inner wall 20 and the straight partition plate 17. It is a position close to the connecting portion of the refrigerant, and is disposed at a position opposite to the refrigerant inlet 21 with the straight partition plate 17 interposed therebetween.

  Of the two C-shaped partition plates, the inner partition plate 16a has an end portion 23a closer to the refrigerant inlet 21 connected to the straight partition plate 17 and an opposite end portion 23b released. It is in the state. On the other hand, the outer partition plate 16b has an end portion 24a closer to the refrigerant discharge port 22 connected to the straight partition plate 17, and the opposite end portion 24b is in a released state.

  Therefore, the inner annular path 18a formed between the center side inner wall 19 and the inner partition plate 16a and the intermediate annular path 18b formed between the inner partition plate 16a and the outer partition plate 16b are connected to each other. An outer ring formed between the outer partition plate 16b and the outer peripheral side inner wall 20 is communicated in (a space formed between the released end portion 23b of the inner partition plate 16a and the straight partition plate 17). The path 18c and the intermediate annular path 18b are in communication with each other in the connecting portion 26 (a space formed between the open end 24b of the outer partition plate 16b and the straight partition plate 17). .

  As shown in FIGS. 2 and 3, heat transfer fins 28 are provided in the inner annular passage 18 a, the intermediate annular passage 18 b, and the outer annular passage 18 c constituting the refrigerant passage 3. Two of each are arranged on a concentric circle. These heat transfer fins 28 are for improving the heat transfer efficiency by increasing the contact area (heat transfer area) with the refrigerant, and their upper ends are all in contact with the ceiling surface of the refrigerant flow path 3. The lower end is installed in contact with the floor surface of the refrigerant flow path 3.

  Next, the operation of the susceptor 2 according to the present invention will be described with reference to FIGS. 1, 2, and 3. In the susceptor cooling system 1 shown in FIG. 1, as described above, the refrigerant is supplied from the refrigerant supply device 4 to the refrigerant flow path 3 of the susceptor 2 through the refrigerant supply pipe 9 (see FIG. 1). It is like that.

  The refrigerant supplied to the refrigerant flow path 3 first flows into the inner annular path 18a from the refrigerant inlet 21 (see FIG. 2). Around the refrigerant inlet 21, the end of the straight partition plate 17 is connected to the center inner wall 19, and the end 23 a of the C-shaped inner partition plate 16 a is connected to the straight partition plate 17. Therefore, the three sides are closed. Therefore, the refrigerant that has flowed into the inner annular passage 18a travels in the circumferential direction (the counterclockwise direction in FIG. 2) around the support shaft 27 of the susceptor 2 through the space between the central inner wall 19 and the inner partition plate 16a. Will do.

  Then, the refrigerant that has made a full circle around the inner wall 19 on the center side of the susceptor 2 and has reached the end 23b of the inner partition plate 16a is prevented from traveling in the circumferential direction by the straight partition plate 17, and thus the communication portion 25. To the intermediate annular path 18b.

  The refrigerant flowing into the intermediate annular path 18b turns (inverts) with the end 23b of the inner partition plate 16a as a turning point, and this time, the space between the inner partition plate 16a and the outer partition plate 16b is reversed. It proceeds in the direction of rotation (the direction of rotation around the support shaft 27 of the susceptor 2 and opposite to the direction of rotation of the inner annular path 18a) (clockwise direction in FIG. 2).

  The refrigerant that has made one round from there and reaches the end 24b of the outer partition plate 16b is prevented from advancing again by the straight partition plate 17 and flows into the outer annular path 18c from the connecting portion 26.

  The refrigerant flowing into the outer annular path 18c is reversed again with the end 24b of the outer partition plate 16b as a turning point, and the space between the outer partition plate 16b and the outer peripheral side inner wall 20 is again rotated in the reverse direction (of the susceptor 2). The traveling direction is the circumferential direction around the support shaft 27 and is the direction opposite to the circumferential direction in the intermediate annular path 18b) (the counterclockwise direction in FIG. 2).

  The refrigerant that has made one round from there is prevented from advancing again by the straight partition plate 17, and is discharged from the refrigerant discharge port 22 that opens near the connection portion between the straight partition plate 17 and the end 24a of the outer partition plate 16b. Then, the refrigerant is returned to the refrigerant supply device 4 through the refrigerant discharge pipe 10 (see FIG. 1).

  As described above, in the present embodiment, the refrigerant introduced into the refrigerant flow path 3 sequentially flows down the inner annular path 18a, the intermediate annular path 18b, and the outer annular path 18c and is discharged from the refrigerant flow path 3. Will be. The refrigerant that has flowed into the intermediate annular path 18b from the inner annular path 18a travels in a direction opposite to the circumferential direction in the inner annular path 18a, and the refrigerant that has flowed into the outer annular path 18c from the intermediate annular path 18b is Furthermore, it proceeds in the reverse direction.

  That is, the refrigerant flowing down the inner annular path 18a and the refrigerant flowing down the adjacent intermediate annular path 18b flow in opposite directions with a thin inner partition plate 16a (about 1 mm thick) (opposite flow). Similarly, the refrigerant flowing down the intermediate annular path 18b and the refrigerant flowing down the outer annular path 18c adjacent thereto are separated by a thin outer partition plate 16b (about 1 mm thick). Will flow as a counterflow. In this way, heat exchange is performed between the refrigerant flowing down as the “opposite flow” via the inner partition plate 16a and the outer partition plate 16b, and therefore, the temperature of the refrigerant in the circulation direction around the support shaft 27 The difference is eliminated, and as a result, the susceptor 2 or the wafer 11 can be uniformly cooled.

  Further, when the refrigerant introduced into the susceptor 2 flows down in the refrigerant flow path 3 in this way, the heat input on the surface of the wafer 11 (see FIG. 3) is changed to the gas layer 15, the electrode sheet 13, and Through the upper part of the susceptor 2, the heat is transferred from the heat transfer surface (the ceiling surface of the susceptor 2, the inner partition plate 16a, the outer partition plate 16b, the heat transfer fins 28, and the floor surface of the susceptor 2) to the refrigerant. .

  At this time, the liquid-phase refrigerant out of the gas-liquid mixed-phase refrigerant boils and evaporates according to the amount of heat transfer, and absorbs heat conducted from the wafer 11 as latent heat. The refrigerant introduced into the refrigerant flow path 3 in the gas-liquid mixed phase initially evaporates all of the liquid phase refrigerant while flowing down in the refrigerant flow path 3. It is discharged from the refrigerant discharge port 22.

  Thus, in the refrigerant flow path 3, “liquid phase refrigerant evaporation”, which is the evaporation process of the refrigeration cycle, is performed. That is, in this susceptor cooling system 1, the susceptor 2 functions as an evaporator. Accordingly, since the susceptor 2 or the wafer 11 can be directly cooled using boiling heat transfer, the cooling efficiency can be dramatically improved as compared with the conventional susceptor cooling system based on the two-stage cooling method.

  In this embodiment, since the susceptor 2 also serves as an “evaporator” as described above, the “evaporator as an independent device” is not included in the susceptor cooling system 1. However, in order to give priority to the uniformity of the cooling temperature in the susceptor 2, an “evaporator as an independent device” (in the case where the susceptor 2 is considered as a “first evaporator”) is used. The susceptor cooling system 1 can also be added.

  When such a second evaporator is provided separately, the vapor phase refrigerant in the susceptor 2 is overheated, so that the temperature of the susceptor 2 partially rises and the uniformity of the cooling temperature is impaired. Can be avoided.

  More specifically, when the refrigerant introduced in the gas-liquid mixed phase state is completely vaporized in the refrigerant flow path 3, the refrigerant (vapor) is not discharged from the time of the complete vaporization until it is discharged out of the susceptor 2. In the (phase state), heat transfer from the wafer 11 cannot be absorbed as latent heat, and is heated according to the amount of heat transfer, and the temperature of the susceptor 2 may rise only by that portion.

  In order to avoid such a problem, the refrigerant is introduced into the refrigerant flow path 3 by adjusting the ratio of the gas-phase refrigerant and the liquid-phase refrigerant so that the refrigerant is completely vaporized immediately before the refrigerant discharge port 22. However, in addition to requiring precise control, it may be affected by changes in various conditions such as the size of the load, so it is extremely difficult to make such subtle adjustments. is there.

  On the other hand, when the second evaporator is prepared separately and provided on the downstream side of the susceptor 2, the refrigerant is not completely vaporized in the refrigerant flow path 3, but is discharged from the refrigerant flow path 3. The refrigerant can be completely vaporized. That is, the introduction ratio of the gas-phase refrigerant and the liquid-phase refrigerant can be adjusted so that the refrigerant is discharged from the refrigerant flow path 3 while the liquid-phase refrigerant remains slightly in the refrigerant (in this case, to some extent) As a result, it is possible to avoid the above-mentioned problems and to make the cooling temperature uniform in the susceptor 2.

  In addition, when being supplied from the refrigerant supply device 4, the refrigerant passes through the expansion valve 7 (see FIG. 1) and is decompressed (squeezed and expanded), and in the state of the refrigerant flow path 3 in the state of wet steam. To be introduced. In some cases, the refrigerator refrigerant is mixed with refrigerant hot gas (high temperature / high pressure gas compressed by the compressor 5) sent through the hot gas bypass 8 after passing through the expansion valve 7. Then, it is introduced into the refrigerant flow path 3.

  As described above, in the present embodiment, the refrigerator refrigerant is introduced into the refrigerant flow path in a wet steam state or in a state in which the refrigerant hot gas is mixed. , Refrigerator refrigerant can be adjusted to a gas-liquid mixed phase state that flows down in a flow form of “annular flow”, and an unfavorable flow form (such as “Churn flow” or “slag flow” vibrates in the refrigerant flow path. It is possible to preferably avoid the refrigerant from flowing down in a flow form that causes

  Next, the results of experiments conducted by the inventors of the present invention on the “susceptor 2” of the present invention will be described.

  First, an attempt was made to verify by experiments whether or not the temperature difference of the refrigerant can be eliminated by devising the structure of the refrigerant flow path 3 and the susceptor 2 or the wafer surface can be cooled uniformly.

  In this experiment, as an embodiment of the present invention, two or three hollow portions formed inside are partitioned by one or two C-shaped partition plates 16 (16a, 16b). Two models (type A and type B) of the susceptor cooling system having the susceptor 2 in which the refrigerant flow path 3 including the two annular paths is formed are prepared. Further, as a comparative example, a hollow portion formed inside is prepared. One model (type X) having a susceptor 2 in which a refrigerant flow path 3 composed of two annular paths is formed by being partitioned by a single C-shaped partition plate 16 is prepared. It carried out by supplying the gas-liquid mixed phase refrigerant | coolant (refrigerator refrigerant | coolant) to the refrigerant | coolant flow path 3 in each.

  Among these, the susceptor 2 of type A (the present invention) is divided into two annular passages (inner annular passages), as shown in FIG. 18a and the outer annular path 18c), and the refrigerant in the inner annular path 18a and the refrigerant in the outer annular path 18c flow in the opposite directions.

  In addition, as shown in FIG. 2, the type B (present invention) susceptor 2 has a hollow portion partitioned by two C-shaped partition plates (inner partition plate 16a and outer partition plate 16b). There are three annular passages (an inner annular passage 18a, an intermediate annular passage 18b, and an outer annular passage 18c), and the refrigerant in the adjacent annular passages is configured to flow in the opposite directions.

  On the other hand, in the susceptor 2 of type X (comparative example), as shown in FIG. 5, the hollow portion is partitioned by a single C-shaped partition plate 16, and two annular passages (inner annular passage 18a, The outer annular path 18c) is configured such that the refrigerant in the inner annular path 18a and the refrigerant in the outer annular path 18c flow down in the same circumferential direction.

  The specific specifications and experimental conditions of these models (types X, A, and B) are as shown in the following table.

  Gas-liquid mixed phase refrigerant (refrigerant refrigerant) is supplied into the refrigerant flow path 3 of the susceptor 2 of each model (type A, type B, and type X) having the above specifications, and the temperature of the wafer surface. Was measured at a plurality of locations, and the maximum value of the temperature difference produced in the circumferential direction was calculated. The results are shown in the following table.

  As shown in Table 2, when a gas-liquid mixed phase refrigerant (refrigerant refrigerant) was supplied to a type X susceptor 2 prepared as a comparative example, a temperature difference of 0.89 ° C. at maximum occurred. On the other hand, in the type A susceptor 2 configured such that the refrigerant in the inner annular path 18a and the refrigerant in the outer annular path 18c flow in the reverse direction, the refrigerant flows in the same circumferential direction. As compared with the type X (comparative example) susceptor 2, the temperature difference generated on the wafer surface could be reduced by about 30%.

  Further, the refrigerant is divided into three annular passages (inner annular passage 18a, intermediate annular passage 18b, outer annular passage 18c) by two C-shaped partition plates (inner partition plate 16a, outer partition plate 16b). In the type B susceptor 2 having the flow path 3, the temperature difference was reduced by about 65% compared to the type X (comparative example) susceptor 2.

  From these results, the refrigerant flow configured such that the refrigerant flowing down is reversed halfway and flows in the reverse direction rather than the refrigerant flow path 3 configured so that the refrigerant always flows in the same circulation direction. It was confirmed that the path 3 can reduce the temperature difference on the wafer surface.

  Furthermore, the refrigerant flow path 3 configured to be partitioned into three annular paths by two C-shaped partition plates is partitioned into two annular paths by a single C-shaped partition plate. It was confirmed that the temperature difference on the wafer surface can be made smaller than that of the configured refrigerant flow path 3. Thus, by devising the structure of the refrigerant flow path 3, it is confirmed that the temperature difference of the refrigerant can be reduced, and as a result, the susceptor 2 or the wafer surface can be cooled uniformly. It was.

Schematic of 1st Embodiment of the susceptor cooling system 1 to which this invention "susceptor 2" is applied. The enlarged view of the horizontal cross section of the susceptor 2 shown in FIG. The enlarged view of the vertical cross section of the susceptor 2 shown in FIG. The enlarged view of the horizontal cross section of the susceptor 2 of the type A used in Example 1 of this invention. The enlarged view of the horizontal cross section of the type X susceptor 2 used as a comparative example.

Explanation of symbols

1: Susceptor cooling system,
2: Susceptor,
3: Refrigerant flow path,
4: Refrigerant supply device,
5: Compressor,
6: Condenser,
7: expansion valve,
8: Hot gas bypass,
9: Refrigerant supply pipe,
10: refrigerant discharge pipe,
11: Wafer,
12: Processing chamber of the etching apparatus,
13: Electrode sheet,
14: Gas supply path,
15: gas layer,
16: Partition plate
16a: inner partition plate,
16b: outer partition plate,
17: Straight partition plate,
18a: inner ring,
18b: intermediate ring road,
18c: outer annulus,
19: Center side inner wall,
20: outer peripheral side inner wall,
21: refrigerant inlet,
22: Refrigerant outlet
23a, 23b, 24a, 24b: ends of partition plates,
25, 26: communication section,
27: support shaft,
28: Heat transfer fin,

Claims (3)

An annular hollow portion formed inside is partitioned by a C-shaped partition plate, thereby forming a refrigerant flow path comprising a plurality of annular paths inside,
The susceptor, wherein the refrigerant flowing down two adjacent annular paths among the plurality of annular paths is configured to flow in opposite directions across the C-shaped partition plate.   The susceptor according to claim 1, wherein two or more C-shaped partition plates are arranged on a concentric circle of an imaginary circle centered on the axis of the susceptor.   The susceptor according to claim 1, wherein heat transfer fins for increasing a heat transfer area are arranged in the plurality of annular passages.

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